Capture of anthropogenic carbon dioxide from large sources of emission such as fossil fuel power plants is a key target in the ongoing effort to mitigate the effect of greenhouse gases on global climate change. Although mature, the liquid phase amine scrubbing technology suffers from inherently high regeneration cost, equipment corrosion and amine oxidative degradation. As a result, there is a strong tendency to develop recyclable solid sorbents to achieve competitive, less energy intensive acid gas removal alternatives.
Most physical CO2 adsorbents such as 13X zeolite, activated carbons, periodic mesoporous silica and metal-organic frameworks (MOFs) require a large pressure and/or temperature gradient between the adsorption and desorption stages to enable both efficient adsorption performances and near complete desorption of CO2. Moreover, they exhibit relatively low selectivity toward CO2, generally low tolerance to water vapour in the gas feed, and their CO2 separation performance decreases drastically by increasing the temperature.
Incorporation of amine groups onto large surface area porous solids via direct synthesis, impregnation, surface polymerization, surface grafting or co-condensation as a promising approach for CO2 capture has gained prominence in recent years. When properly designed, such materials exhibit high adsorption capacity, fast CO2 adsorption and desorption and low energy recycling requirement.
In addition to the above-mentioned attributes, amine-containing materials are tolerant to the occurrence of moisture in the feed. Actually, CO2 adsorption is enhanced by the presence of moisture in the feed (Serna-Guerrero et al. 2008). The reason lies within the nature of the amine —CO2 interactions. Under dry adsorption conditions, surface amine groups interact with CO2 to form carbamate with a stoichiometric CO2/N ratio of 0.5, whereas under proper humidity conditions, bicarbonate with a stoichiometric ratio CO2/N=1 may be formed (Serna-Guerrero et al. 2008). In contrast, in the presence of other adsorbents such as zeolites and activated carbons, CO2 adsorption is inhibited by moisture because of unfavourable competition.
However, despite the large number of contributions devoted to CO2 adsorption over amine-containing materials (Choi et al. 2009), and despite the utmost importance of the long term stability of such materials, no studies addressed the issue of adsorbent stability through extensive recycling.
The lifetime of adsorbents, which determines the frequency of their replacement, is a critical parameter of equal importance as CO2 adsorption capacity, selectivity and kinetics, having a direct impact on the economics of any commercial scale operation.
This background information is provided for the purpose of making known information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.